One common theme is power and ambition. Both Madara and Obito are characters with great power and strong ambitions in the Naruto series, and fanfics often explore how their relationship is influenced by these aspects.
The theme of redemption also appears. Given some of the actions of Obito and Madara in the Naruto series, fanfics sometimes explore if they can find redemption in their relationship with each other. They might try to make up for their past mistakes through their connection in the fanfic.
Madara could also save Naruto by using his knowledge of the ninja world. Maybe he has some inside information about a plot against Naruto and he intervenes in time to stop it. He might have discovered a secret plan by an enemy group and takes action to keep Naruto out of harm's way. This could involve manipulating events behind the scenes or directly confronting the threat.
A third option is 'The Alliance of Obito and Madara'. In this one, the author focuses on their combined power and how they could have ruled the ninja world together. It's full of action scenes and also has some deep emotional moments between the two characters.
In such a fanfiction, the story could take a very dark turn. Naruto's ideals of friendship and peace might be severely tested. He could be forced to question his own beliefs as Obito and Madara have very different outlooks. Maybe Naruto would try to change their minds, but it would be extremely difficult as they are both very set in their ways of achieving a new world order through more extreme means.
Well, it could be a fan - made story where Sakura, from the Naruto series, plays a crucial role in saving Obito. Maybe it involves her using her medical ninjutsu skills to heal him from some critical injury or her strong will to bring him back from the dark side he was on.
There's a fanfic called 'Obito's New Path'. In it, Obito has a change of heart after seeing Naruto's unwavering belief in friendship. He decides to save Naruto from a dangerous plot by some rogue ninja. The story delves into Obito's internal struggle as he tries to make up for his past mistakes while saving Naruto.
One possible plot could be that Obito arrives just in time to save Rin from being captured by enemy ninjas. He uses his Sharingan abilities to outwit the enemies and then escapes with Rin. Maybe he has to fight through a horde of strong opponents, but his determination to save Rin gives him the strength to persevere.
One potential antagonist could be the Hidden Mist ninjas. They are known for their ruthless tactics, and they might target Rin for some strategic reason. Maybe they think she has valuable information about Konoha's defenses.
Fanfiction.net is also a good place to look for madara x obito fanfic. There are many different stories written by fans from all over the world. However, the quality may vary, so you might need to read the summaries and reviews before choosing one.